Session I

Monday, May 22nd

Session I

T1

Quantifying Analyte-Porous Silicon Interactions

Ari Darlow Justin M. Reynard, Dustin T. McCall, Frank V.
Bright

University at Buffalo, Department of Chemistry

Porous silicon (pSi) has been studied for use in
chemical sensing. Key to the success of such a strategy is to understand and
selectively control analyte-pSi interactions. Toward these ends, we have been
using the intrinsic pSi photoluminescence (PL) to determine the
analyte-dependent PL response from as prepared and oxidized pSi (ap-, ox-pSi).
Although these experiments provide some insights, they do not provide details
into exactly how the analyte interacts with the Si nanocrystallites. To rectify
this issue we have performed time-dependent Fourier transform infrared (FTIR)
experiments under analyte flow to following the effects of analyte uptake and
release within the pSi matrix and on the nanocrystallite surface Si-O-Si and
SiHx (x = 1-3) residues. The combination of PL and FTIR experiments allow us to
determine how the analyte interacts with the nanocrystallites to yield the
analyte-dependent PL response. This presentation will summarize our most recent
experiments.

According to the Environmental Protection Agency,
over one billion pounds of pesticides are used in the United States
annually. Organonitrogen pesticides are
currently amongst the most prevalently employed pesticide classes. However, little is known about how interactions
with, and modifications catalyzed by, leaf and soil surfaces affect their
environmental fate. Here, two such
pesticides, carbaryl and propoxur are studied via SFG vibrational spectroscopy
at the air/solid interface after being deposited on a fused quartz substrate,
which serves as a model system for soil silica.
Despite being similar in structure and composition, the results obtained
thus far suggest that the two pesticides interact with mineral surfaces differently,
with carbaryl exhibiting a greater propensity for self-assembling into
supramolecular aggregates than propoxur."

The synthesis and applications of dye molecules has
fascinated chemists for over a century.
Applications of synthetic dyes are vast, and are of interest to textile
industry, molecular imaging, and renewable imaging. Recent developments in biomedical imaging and
materials chemistry has necessitated the synthesis of tailored designer
dyes. Specifically, Surface-Enhanced
Raman Scattering (SERS) requires spectroscopically unique chromophores to
permit multiplexing of convoluted biological tissues. Currently, the user is limited to a handful
of commercially available dyes, precluding the true multiplexing capabilities
of SERS from being realized. The
pyrylium dye class has long been known, and possess several functionalizable
moieties that enable control over photophysical and photochemical
properties. Namely, the incorporation of
heavy chalcogen atoms confer affinity for gold and silver nanopoarticles
typically used in SERS assays.
Furthermore, these dyes can be tailored to incorporate several different
Raman active functional groups, enabling synthesis of spectroscopically unique
dyes. An additional benefit is that the
absorption of these pyrylium dyes can be tuned from the near infrared to
infrared. Compatibility with NIR
excitation sources permit deep tissue penetration and minimizes scattering from
biological tissue. Herein, the synthesis of novel near infrared absorbing
pyrylium will be described.

T5

Impact of Laser Exposure and Power on Single- and Few-Layer WS2

Samantha Matthews, Chuan Zhao, Hao Zeng
and Frank V. Bright

University at Buffalo,
Department of Chemistry

Single- and few-layer transition metal
dichalcogenides (TMDCs) are mainly characterized by layer thickness, chemical
composition, and exciton contribution using atomic force microscopy (AFM),
Raman, and photoluminescence (PL) techniques, respectively. Raman and PL
measurements necessitate that the sample be exposed to laser radiation for
various time periods. What is the impact of laser power and time on the WS2?
This presentation will summarize recent research exploring the role of laser
power and exposure time on the observed PL emission, Raman spectra, and
topography from WS2 on sapphire.